Circuit-closer for locks



J. SCHWARTZ.

CIRCUIT CLOSER FOR LOCKS.

APPLICATION FILED JUNE 28,1919.

1,358,254, PatentedNov. 9,1920.

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INVENTOR Its distinguishing UNITED STATES JOHN SCHWARTZ, 0F DONOR-A, PENNSYLVANIA.

CIRCUIT-CLOSER FOR LOCKS.

Application filed June 28, 1919.

To all whom it "may concern:

Be it known that I, JOHN SCHWARTZ, residing at Donora, in the county of VVashington and State of Pennsylvania, an applicant for United States citizenship, heretofore a subject of the King of Hungary, have invented or discovered certain new and useful Improvements in Circuit-Closers for Locks, of which improvements the following is a specification.

My invention relates to improvements in locks, and has as its particular object the provision of a burglar alarm. The lock and its proper key are so constructed that the key will not operate the alarm. but a key not especially adapted for the locka key such as a burglar might use in attempting to pick the lock-will sound the alarm.

The invention is illustrated in the accompanying drawings, in which Figure .1 is a view in vertical section of an ordinary lock in place in a door, this lock having applied to it the burglar alarm of my invention. Fig. 2 is a view in vertical section on the line II-II, Fig. 1, and in this View the key which belongs to the lock is shown in place in the keyhole. Fig. 3 is a diagrammatic view showing the electric connections of the burglar alarm. Fig. 4 is a view in elevation of a key not adapted to the lock, but a key such as will sound the alarm.

The lock, as has been said, is, generally speaking, a lock of familiar construction. feature lies in this, that within the casing 7, and surrounding the keyhole, are successive concentric plates 1 and 2 of insulating and conducting ma terial. Referring particularly to Fig. 3 it will be seen that these plates are concentrically arranged with respect to the keyhole. The order of succession of these plates is, manifestly. not an essential matter, but I prefer the order shown, the plates of insulation 1 being arranged within the encircling plates 2 of conducting material. The two plates of conducting material 2 are insulated from the casing 7 of the lock which carries them, and are electrically connected one to the other. A battery 3 or equivalent source of current, has a lead from one pole connected to one of the plates 2 and a lead from the other pole connected to the metallic casing 7 of the lock. A signal device, which may be of any nature desired, and which is shown in the form of an electric bell 4, is arranged in the circuit. Normally the circuit Specification of Letters Patent.

Patented Nov. 9, 1920. Serial No. 307,298.

is not closed, for it is interrupted by the layers of insulation which lie between plates 2 and the lock casing. The circuit can be closed (and the signal operated) onl through a key introduced into the keyhole, and making contact along its shank with the lock casing 7 and through its bit with one or both of the plates 2.

The key intended for the lock is shown in place within the lock in Fig. 2, and a key of ordinary construction, not intended for the lock, is shown separately in Fig. 4. Comparing the two keys it Will be observed that the bit of the key intended for the lock is recessed or oflset at points opposite the plates 2, 2, while the key not intended for the lock the ordinary keyis not so recessed. It will furthermore be observed that the recessing of the key intended for the lock leaves shoulders 5 upon the bit, which shoulders bearing upon the plates 1 of insulating material prevent the recessed portions from making contact with the plates 2. A key such as that shown in Fig. 4 however, when introduced into the lock, will make contact along its shank with the rim of the key-hole (that is, with the lock casing 7) and through its bit with one or both of the plates 2, thus closing the circuit and giving alarm.

It will thus be seen that the key intended for the lock will be introduced into the keyhole and will be turned to unlock the lock without sounding the alarm, but that any key not so recessed-a key such as that shown in Fig. 4:, for exampleif introduced into the lock and turned, will engage one of the plates 2 on one side or the other, and, necessarily engaging by its shank the casing of the lock, will close the circuit and sound the alarm.

I claim as my invention:

1. A lock for a door including in combination a casing of conducting material provided with a keyhole, a pair of contacting plates of conducting material borne by the opposite walls of the casing, insulated from the casing, and arranged adjacent the keyhole, and terminals for an electric circuit, of which one terminal is mounted on said casing and the other terminal is connected to one of the said plates, the two said plates being connected together in series, substantially as described.

2. A lock for a door including in combination a lock casing of conducting material provided With a keyhole, terminals for an electric circuit, one of which terminals is mounted on said casing, plates'of insulating and of conducting material of unequal lateral extent facing the lock casing Within and surrounding the keyhole, the insulating plate lying between the plate of conducting material and the lock casing, the plate of conducting material being connected With the other terminal of sald circuit, and a cooperatlng key havlng its bit recessed 1n correspondence with the arrangement of the plates of conducting and of insulating material surrounding the keyhole, substantially as described.

In testimony whereof I have hereunto set my hand.

JOHN SCHWARTZ.

Witnesses. 7

PAUL N. CRITOHLOW, FRANCIS J. ToMAssoN. 

